3-azabicyclo(3.1.0)hexane-2-carboxylic acid, also known as methanoproline, and certain of its esters, are known to inhibit (suppress) pollen formation in cereal grains: U.S. Pat. No. 4,047,930 (the acid being designated therein as 2-carboxy-3,4-methanopyrrolidine). Methanoproline exists in the forms of two geometric (i.e., cis and trans) isomers. Each of these isomeric forms exists in the forms of optical isomers. The racemic mixtures of both of the geometric isomeric forms inhibit pollen formation in cereal grains. However, it has been found that with respect to some cereal grains the cis racemate is more active for that purpose than the trans racemate. Accordingly, it is desirable that there be available a method for preparing the cis racemate of methanoproline.